ABSTRACT
Three common and potentially errorless stimulus-control procedures are fading (Terrace, 1963a), superimposition (Terrace, 1963b), and stimulus shaping (Bijou, 1968 and Sidman and Stoddard, 1966). The successful use of these three procedures depends on the programmer’s choice of the right element of the stimulus to emphasize at any given time. Various experimenters have suggested effective methods for choosing the correct element. Bijou (1968) has argued that in the absence of research showing which of the many possible fading techniques should be used, the part of the stimulus containing “the cue essential to the discrimination” should be the one manipulated. Newman’s study with pigeons, reported by Baron (1965), indicated that one should eliminate any other cue in the stimulus that is not critical to the final discrimination, especially if that cue is higher in the organism’s attending hierarchy than the critical cue. In other words, there may be some cues in a stimulus complex that are more readily responded to (color as opposed to white lines, with pigeons for example), due to the nature of the organism or its past history. These cues, although readily responded to, nevertheless may not aid a final discrimination. If such a cue is within the initial stimulus complex, then the organism may attend to it and not to the critical cue.
